Electron tube



y 7, 1953 D. F. nmEscHMAfi zrAi. 2,644,907

'fiECTRON TUBE Filed May 7, 1951 BY Emi/ E Wests/1b r ATTORNEYINVENTORS' Donald E Dn'es/rman Patented July 7, 1953 2,64%90'7 ELECTRONTUBE:

Donald F. Drieschman, Los Altos, and Emil F.

Wesenberg,

San Bruno, Calif., assignors to Eitel-McCullough, Inc., San Bruno,Calif., a corporation of California Application May 7, 1951, Serial No.224,952

Our invention relates to an electron tube of the type having coaxialterminals, and more particularly to improvements in the envelopestructure of such tube.

The principal object of our invention is to provide a tube wherein themetal terminal parts of the envelope are separated by ceramic pieces.

Another object is to provide an envelope and electrode mountingconstruction specially adapted for ceramic-to-metal sealing techniques.

A further object is to provide an envelope of the character describedfor a tube having planar type electrodes.

The invention possesses other objects and features of advantage, some ofwhich, with the foregoing, wil1 be set forth in the followingdescription of our invention. It is to be understood that we do notlimit ourselves to this disclosure of species of our invention, as wemay adopt variant embodiments thereof within the scope of the claims.

Referring to the drawing, the single figure is an axial sectional viewof a tube embodying the improvements of our invention.

In terms of broad inclusion, our improved tube comprises an envelope ofgenerally cylindrical shape enclosing electrodes such as a cathode, gridand anode, these electrodes preferably having active surfaces disposedin parallel planes. Terminals for the electrodes comprise cylindricalmetal members forming part of the envelope, which terminals are arrangedin coaxial alignment. The terminals are separated and electricallyinsulated. by cylindrical ceramic sections also forming part of theenvelope and connected to the terminal members by ceramic-to-metalbrazes.

In our preferred construction, the grid mount and cathode stem aredesigned for insertion in the grid terminal member and the finalseal ismade by a metallic bond.

In greater detail and referring'to the drawing, our improvements areillustrated by a triode structure comprising an anode 2, grid 3 andcathode 4 having active surfaces disposed in parallel planes. Metalanode 2 at the upper end of the tube envelope has an inwardly projectingportion having a flat end face presented interiorly of the envelope andan outwardly projecting portion carrying a suitable cooler 6. The anodealso carries the metal exhaust tubulation I which communicates with theenvelope through passage 8, the tubulation beingpinched off at tip 9after evacuation of the envelope.

Cathode 4 at the lower portion of the envelope 8 Claims. (01. 313249) isof the indirectly heated type and comprises a cup-shaped metal sleevehaving a flat-upper surface coated with a suitable electron emissivematerial. The heater II for the cathode comprises a coil disposed withinthe cathode sleeve and is preferably surrounded by a suitable heatshield I2. Grid 3 is of the disk type having parallel wire bars lying ina plane parallel with the opposing ends of the anode and cathode.

Coaxial metal terminals are provided on the envelope for the electrodes,including an upper anode terminal 13, a cathode terminal on the stemstructure [4 and an intermediate grid terminal it. These terminals arearranged coaxially of the envelope and present external contact surfaceshaving different diameters of which the anode contact surface is thelargest, the grid surface the next largest and the cathode surface thesmallest. This terminal arrangement permits plugging the tube into asocket.

In our improved tube, the electrode terminals are separated andelectrically insulated by coaxial cylindrical ceramic sections includinga section I! interposed between the grid and anode terminals and asection l8 interposed between the grid and cathode terminals. Theceramic sections thus forming portions of the envelope are united to theadjacent metal parts by metallic bonds, such as ceramic-to-metal brazes,to establish vacuum-tight joints.

The ceramic used in making up the envelope sections may be of anysuitable ceramic-like material such as the alumina or zircon typeceramic bodies commercially available. We prefer the alumina or zircontype bodies because of their good mechanical strength, thermalresistance and electrical insulating properties.

The ceramic-to-metal bonds forming the vacuum-tight seals may be made inseveral ways utilizing known metalizing and brazing techniques- Forexample, the surfaces of the ceramic piecesm-ay be coated with finelydivided molybdenum powder, or a mixture of molybdenum and'iron powdersor the like, and fired in hydrogen to a temperature of about 1500 C. tosinter the metal powder to the ceramic surface. This produces a thinmetallic layer firmly bonded to the ceramic. Such metalized surfaces maythen be brazed or soldered to adjacent metal parts with silver solder orbrazing alloys such as silver-copper, gold-copper or the like. Thebrazes are readily made by fitting the metalizedceramic surfaces againstthe metal parts with rings of wire solder adjacent the joints, andthenelevating the temperature of the whole up to the melting point ofthe solder in a suitable furnace. Another metalizing technique is topaint titanium or zirconium hydride powders on the surfaces of theceramic parts and fire in vacuum to about 1200 C., after which themetalized surfaces may be brazed with silver solder of the like.

The metal terminal construction in our tube is specially designed forthe ceramic sections employed in the envelope structure. As shown, theanode terminal member 13 comprises a cupshaped member having a bottomwall [9 surrounding anode 2 and a cylindrical flange 2| forming thecontact surface of the terminal. This terminal member is united to theanode at braze 22. The bottom wall I9 is formed with a re-entrantportion for receiving the ceramic section and to provide a downturnedlip 23 engaging the outer peripheral edge of ceramic cylinder ll. Inthis case, the ceramic is metalized along both the upper and outerperipheral surfaces and the brazing material 24 extends over both ofthese areas so that the ceramic is brazed to the flat bottom wall It, aswell as to the downturned lip 23. This provides an extremely strongjoint construction which is especially important at this end of the tubecarrying the relatively heavy anode and cooler structure.

The grid terminal member [6 is tubular in shape and has an outturnedflange 26 with an upturned lip 2'! for engaging the outer periph eraledge of ceramic cylinder l1. Here again the ceramic section is metalizedalong both the lower and outer peripheral surfaces and the brazingmaterial 28 extends over both of these areas, namely, at the flange 26,as well as along the lip 27.

Cathode stem M includes a tubular metal stem member 23 which comprisesthe cathode terminal. This stem structure is so designed that thecathode may be completely mounted on the stem and the entire unitinserted into the tube through the tubular grid terminal 16. For thispurpose the cathode stem includes a supporting sleeve 3d which slidablyfits into the lower end of the grid terminal member. Sleeve 30 ispreferably of o -shape to provide a downturned lip 3*! engaging theupper peripheral surface of ceramic section it. This peripheral surfaceis metalized and brazed at 32 to lip 3!. An outwardly extending flange33 brazed on stem member 29 has an upturned lip 34 engaging the lowerperipheral surface of the ceramic section, the lower edge and peripheralsurface of the ceramic being ineitolic e l and brazed as indicatedat'36.

Cathode sleeve 6 is connected to and supported directly by the upper endof stem member 29. (inc end of the heater coil H is also connected tothe tubular member 25, which stem member thus functions a cathodeterminal as well as one of the connections for the heater. In order toprovide the other heater connection, an inner stein member iii isprovided coaxial with the outer member 23, the inner member 31 beingpreferably an inverted cup-shaped metal piece located at the lowerportion of the stem structure. A cylindrical ceramic section 38 isinterposed between the inner and outer stem members. Brazing flanges forthe ceramic are provided by a downwardly extending sleeve 39 on theouter stem member and an upwardly extending sleeve 4! on the inner stemmember. Sleeve 3Q is brazed to the upper end of tubular member 23 andsleeve 4| is preferably a cupshaped piece secured to the top of theinner member 31. These sleeves engage the outer peripheral surfaces ofthe ceramic section, the latter being metalized and brazed at 42 and 43.A rod 44 connects the end of heater coil H to the inner terminal member31.

The stem structure is completed by an insulating sleeve 45 insertedbetween terminal members 29 and 31, this being merely a spacer sleeveand not relied upon as part of the evacuated envelope since thevacuum-tight wall is formed by the ceramic section 38.

Grid 3 is supported by a cylindrical mount 46 having a depending flange4'! adapted for insertion into the tubular grid terminal [6. In thefabrication and assembly of our tube the upper anode portion of theenvelope is completed, including the brazing of ceramic section 11 inplace between the anode and grid terminal pieces I3 and [6. At thisstage of assembly the envelope is open at the lower end of grid terminal[6. The cathode stem portion of the tube is completed apart from therest of the tube, the ceramic sections it and 38 being brazed inposition during stem fabrication. After the heater and cathode have beenmounted on the stem, the stem structure is ready for the final tubeassembly.

The grid 3 on its mount 46 is then inserted into the grid terminal [6,the lower edge of mount 48 being brought into registration with thelower edge of the grid terminal. Cathode stem [4 is then inserted intothe grid terminal, within the cylindrical grid mount, until the loweredge of support 36 registers with the lower edges of the grid mount andgrid terminal. The three registering edges are then simultaneouslybonded together at braze 48.

We claim:

1. An electron tube comprising an envelope, electrodes in the envelopeincluding an anode and grid cathode, coaxial metal terminals on theenvelope for the electrodes, a ceramic section interposed between thegrid and anode terminals, and metallic bonds uniting the ceramic sectionto said terminals, the anode terminal having a ie-entrant portion forreceiving the ceramic secion.

2. An electron tube comprising an envelope, electrodes in the envelopeincluding an anode and grid and cathode, coaxial metal terminals on theenvelope for the electrodes, a ceramic section interposed between thegrid and anode terminals, and metallic bonds uniting the ceramic sectionto said terminals, the anode terminal being cupshaped and having are-entrant bottom portion for receiving the ceramic section.

3. An electron tube comprising anenvelope, electrodes in the envelopeincluding an anode and grid and cathode, coaxial metal terminals on theenvelope for the electrodes, a ceramic section interposed between thegrid and anode terminals and metallic bonds uniting the ceramic sectionto said terminals, the anode terminal havmg a re-entrant portionproviding a downturned lip engaging the upper end of the ceramic sectionand the grid terminal having a flange with an upturned lip engaging thelower end of said ceramic section.

4. An electron tube comprising an envelope, electrodes in the envelopeincluding an anode and grid and cathode, a tubular metal grid terminalon the envelope, a cathode stem comprising a metal stem member coaxialwith the grid terminal, a metal supporting sleeve having an edgeregistering with the lower edge of the grid terminal, a ceramic sectioninterposed between the stem member and said supporting sleeve, saidceramic section having an inner diameter larger than the outer diameterof the stem member, metallic bonds uniting the ceramic section to saidstem member and sleeve, and a metallic bond uniting the registeringedges of said sleeve and grid terminal.

5. An electron tube comprising an envelope, electrodes in the envelopeincluding an anode and grid and cathode, a tubular metal grid termnialon the envelope, a cathode stem comprising a metal stem member coaxialwith the grid terminal, a metal supporting sleeve having an edgeregistering with the lower edge of the grid terminal, a ceramic sectioninterposed between the stem member and said supporting sleeve, saidceramic section having an inner diameter larger than the outer diameterof the stem member, metallic bonds uniting the ceramic section to saidstem member and sleeve, and a metallic bond uniting the registeringedges of said sleeve and grid terminal, said supporting sleeve being U-shaped to provide a downturned lip engagin the upper end of the ceramicsection.

6. An electron tube comprising an envelope, electrodes in the envelopeincluding an anode and grid and cathode, a tubular metal grid terminalon the envelope, a cathode stem comprising a metal stem member coaxialwith the grid terminal, a metal supporting sleeve having an edgeregistering with the lower edge of the grid terminal, a ceramic sectioninterposed between the stem member and said supporting sleeve, saidceramic section having an inner diameter larger than the outer diameterof the stem member, metallic bonds uniting the ceramic section to saidstem member and sleeve, and a metallic bond uniting the registeringedges of said sleeve and grid terminal, said supporting sleeve being U-shaped to provide a downturned lip engaging the outer peripheral surfaceat the upper end of the ceramic section and said stem member having aflange with an upturned lip engaging the outer peripheral surface at thelower end of the ceramic section.

'7. An electron tube comprising an envelope, electrodes in the envelopeincluding an anode and grid and cathode, a tubular metal grid terminalon the envelope, a cathode stem comprising a metal stem member coaxialwith the grid terminal, a metal supporting sleeve having an edge insubstantial registry with the lower edge of the grid terminal, a ceramicsection interposed between the stem member and said supporting sleeve,metallic bonds uniting the ceramic section to said stem member andsleeve, a grid mount having a depending flange lying between said sleeveand grid terminal and having an edge registering with the lower edgesthereof, and a metallic bond uniting the registering edges of saidsleeve and flange and grid terminal.

8. An electron tube comprising an envelope, electrodes in the envelopeincluding an anode and grid and cathode, a tubular metal grid terminalon the envelope, a cathode stem comprising inner and outer stem memberscoaxial with the grid terminal, a ceramic section interposed between thestem members, and metallic bonds uniting the ceramic section to saidstem members, the outer stem member having a downwardly extending flangeproviding a lip engaging the upper end of the ceramic section and theinner stem member having an upwardly extending flange providing a lipengaging the lower end of said ceramic section.

DONALD F. DRIESCHMAN. EMIL F. WESENBERG.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,431,226 Berkey et a1 Nov. 18, 1947 2,446,269 Drieschman Aug.3, 1948 2,456,714 Law Dec. 21, 1948

